MongoDb 在包含多个 json object 的嵌套数组上找到操作

Question

I'm having dataset in which json consists of array having multiple json in it.

The objects in the array have 4 keys, out of which 1 is missing in some of them.

I want to get the documents where all the objects in an array are missing the key.

eg, From these following documents:

{"test":1,desc:[{"price":1,"abc":"def"},{"price":2,"ac":"def"}]}
{"test":1,desc:[{"price":1,"abc":"def"},{"ac":"def"}]}
{"test":1,desc:[{"abc":"def"},{"ac":"def"}]}

I want to match only the last document.

Thanks in advance..

Answer 1

You can just use $exists :

db.collection.find(
    {
        "desc.price": {$exists: false}
    }
)

And if you want for other fields as well:

db.collection.find(
    {
        $or: [
            {
                "desc.price": {$exists: false}
            },
            {
                "desc.abc": {$exists: false}
            },
            {
                "desc.ac": {$exists: false}
            }
        ]
    }
)

One thing to note is that an empty array, ie desc = [] will always be matched by this query. if you want to ensure there's atleast one object use this query:

db.collection.find(
    {
       $and: [
           {
               "desc.price": {$exists: false}
           },
           {
               "desc.0": {$exists: true}
           }
       ]
    }
)

Answer 2

Achieved that, just made a script where i used an array to store the price thing and then used.every method for price to be undefined, it returned me the desired result which i want.